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| United States Patent |
5,198,492
|
|
Stack
|
March 30, 1993
|
Low viscosity, fast curing binder for cellulose
Abstract
Low viscosity, fast curing binders for nonwoven cellulosic materials
comprise an aqueous dispersion of discrete particles of a highly
functionalized emulsion copolymer resulting from the copolymerization of a
water insoluble olefinic non-ionic organic compound, a water soluble
olefinic carboxylate compound and a water soluble olefinic hydroxy ester
or a water soluble olefinic amide or a mixture of hydroxy ester and amide.
The emulsion copolymer dispersion is admixed with a latex to provide a
binder having a relatively low viscosity and capable of reaching about 80
percent of fully cured wet tensile strength in 8 seconds or less.
| Inventors:
|
Stack; Dennis P. (Santa Ana, CA)
|
| Assignee:
|
Rohn and Haas Company (Philadelphia, PA)
|
| Appl. No.:
|
590289 |
| Filed:
|
September 28, 1990 |
| Current U.S. Class: |
524/501; 524/552; 524/555; 524/558; 524/560 |
| Intern'l Class: |
C08J 003/03 |
| Field of Search: |
526/318.25,318.44,307.5,501
524/555,558,560,556
|
References Cited
U.S. Patent Documents
| 3137589 | Jun., 1964 | Reinhard et al. | 117/140.
|
| 3594337 | Jul., 1971 | Shea | 260/17.
|
| 3616166 | Oct., 1971 | Kelley | 161/148.
|
| 3766112 | Oct., 1973 | Blackford | 260/28.
|
| 4289676 | Sep., 1981 | Czauderna et al. | 206/29.
|
| 4406660 | Sep., 1983 | Beiner et al. | 526/317.
|
| 4455341 | Jun., 1984 | Fink et al. | 428/265.
|
| 4743498 | May., 1988 | Kedrowski | 428/288.
|
| Foreign Patent Documents |
| 0224736 | Oct., 1987 | EP.
| |
| 44-22749 | Sep., 1969 | JP.
| |
Primary Examiner: Schofer; Joseph L.
Assistant Examiner: Smith; Jeffrey T.
Attorney, Agent or Firm: Vouros; James G.
Parent Case Text
This application is a division of application Ser. No. 310,245, filed Feb.
13, 1989, which is now pending.
Claims
I claim:
1. A fast curing binder for nonwoven cellulosic materials, said binder
comprising an aqueous dispersion of discrete particles of a highly
functionalized emulsion copolymer formed by the compolymerization of a
mixture of comonomers comprising;
(1) one or more water insoluble polymerizable olefinically unsaturated
non-ionic organic compounds;
(2) one or more water soluble olefinically unsaturated organic compounds
having at least one carboxylate group therein; and
(3) one or more water soluble olefinically unsaturated carboxylic acid
hydroxy esters or water soluble olefinically unsaturated amides or a
mixture thereof; said aqueous dispersion of discrete particles of highly
functionalized emulsion copolymer being admixed with a latex selected from
the group consisting of styrene-butadiene resin (SBR) copolymer latexes,
vinyl acetate/acrylate copolymer latexes, and all-acrylate copolymer
latexes.
2. A binder according to claim 1 wherein said latex is a "zero"
formaldehyde SBR latex.
3. A binder according to claim 1 wherein said aqueous dispersion of
discrete particles of highly functionalized emulsion copolymer is admixed
in an amount of about 3 percent to about 15 percent, by weight, with a
latex.
4. A binder according to claim 1 wherein said aqueous dispersion of
discrete particles of highly functionalized emulsion copolymer is admixed
in an amount of about 5 percent to about 12 percent, by weight, with a
latex.
5. A binder according to claim 1 wherein the particle size of said discrete
particles of highly functionalized emulsion copolymer is in the range of
about 100 nm to about 2100 nm.
6. A binder according to claim 1 wherein the pH of said aqueous dispersion
of discrete particles of highly functionalized emulsion copolymer is about
pH 1.0 to about pH 4.5.
7. A binder according to claim 1 wherein the viscosity of said aqueous
dispersion of discrete particles of highly functionalized emulsion
copolymer is about 5 cps to about 100 cps at solids contents of about 1
percent to about 50 percent.
8. A binder according to claim 1 wherein the solids content of the
admixture of emulsion copolymer and latex is about 5 percent to about 40
percent.
9. A binder according to claim 1 wherein the viscosity of the admixture of
emulsion copolymer and latex is less than about 600 cps at a solids
content of about 30 percent and a pH value of up to about pH 6.
10. A binder according to claim 1 wherein the viscosity of the admixture of
emulsion copolymer and latex is less than about 1200 cps at a solids
content of about 35 percent and a pH value of up to about pH 6.
11. A fast-curing binder for nonwoven cellulosic materials, said binder
comprising an aqueous dispersion of discrete particles of a highly
functionalized emulsion copolymer formed by the copolymerization of a
mixture of comonomers comprising:
(1) one or more water insoluble polymerizable olefinically unsaturated
non-ionic organic compounds having the general formula:
##STR9##
wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected
from hydrogen, halogen, nitro, amino and organic radicals;
(2) one or more water soluble olefinically unsaturated organic compounds
having at least one carboxylate group, said compounds having the general
formula:
##STR10##
wherein R.sub.5, R.sub.6, and R.sub.7 are independently selected from
hydrogen, halogen, nitro, amino, and organic radicals; R.sub.8 is hydrogen
or an organic radicals; and X is an organic radical or a covalent bond;
and
(3) a member selected from the group consisting of one or more water
soluble olefinically unsaturated carboxylic acid hydroxy esters of the
general formula:
##STR11##
wherein R.sub.9, R.sub.10 and R.sub.11 are independently selected from
hydrogen, halogen, nitro, amino, and organic radicals; and R.sub.12 is an
organic radical having at least 2 carbon atoms, with at least one of
R.sub.9, R.sub.10, R.sub.11 and R.sub.12 being an organic radical
containing a hydroxyl substituent, said hydroxyl substituent being located
on a carbon atom which is at least 2 carbon atoms away from the
carboxylate group; and Y is an organic radical or a covalent bond; and one
or more water soluble olefinically unsaturated amides having the general
formula:
##STR12##
wherein R.sub.13, R.sub.14 and R.sub.15 are independently selected from
hydrogen, halogen, nitro, amino, and organic radicals; R.sub.16 and
R.sub.17 are hydrogen or organic radicals; and Z is an organic radical or
a covalent bond; and a mixture of said one or more water soluble
olefinically unsaturated carboxylic acid hydroxy esters and said one or
more water soluble olefinically unsaturated amides;
said aqueous dispersion of discrete particles of highly functionalized
emulsion copolymer being admixed with a latex to produce said binder, the
latex being selected from the group consisting of styrene-butadiene resin
(SBR) copolymer latexes, vinyl acetate/acrylate copolymer latexes, and
all-acrylate copolymer latexes.
12. A binder according to claim 11 wherein:
the total number of carbon atoms in the non-ionic organic compound does not
exceed 30;
the total number of carbon atoms in the carboxylate group containing
organic compound does not exceed 30, with the total number of carbon atoms
in R.sub.8 not exceeding 10 and the total number of carbon atoms in X not
exceeding 10;
R.sub.9, R.sub.10 and R.sub.11 are independently selected from hydrogen,
halogen, nitro, amino and organic radicals containing no more than 10
carbon atoms; R.sub.12 is an organic radical containing from 2 to 10
carbon atoms, and where one or more of R.sub.9, R.sub.10 and R.sub.11 are
organic radicals containing a hydroxyl substituent, R.sub.12 is an
unsubstituted hydrocarbyl radical containing no more than 10 carbon atoms;
and the total number of carbon atoms in Y does not exceed 10; and
R.sub.16 and R.sub.17 are hydrogen or organic radicals containing no more
than 6 carbon atoms; and the total number of carbon atoms in Z does not
exceed 10.
13. A binder according to claim 11 wherein R.sub.1, R.sub.2 and R.sub.3 are
independently selected from hydrogen, aryl, alkylaryl, arylalkyl,
cycloalkyl, straight chain alkyl groups and branched chain alkyl groups
containing no more than 10 carbon atoms; and
R.sub.4 is selected from hydrogen, aryl, alkylaryl, arylalkyl, cycloalkyl,
straight chain alkyl groups containing no more than 10 carbon atoms,
branched chain alkyl groups containing no more than 10 carbon atoms, and
the radical
##STR13##
wherein R.sub.18 is selected from aryl, alkylaryl, arylalkyl, cycloalkyl,
straight chain alkyl groups containing no more than 21 carbon atoms,
branched chain alkyl groups containing no more than 21 carbon atoms; and
polyalkylene ether containing no more than 21 carbon atoms.
14. A binder according to claim 11 wherein R.sub.1 and R.sub.2 are
hydrogen, R.sub.3 is hydrogen or methyl, and R.sub.4 is a member selected
from the group consisting of phenyl, substituted phenyl, and the radical
##STR14##
wherein R.sub.18 is a member selected from the group consisting of
straight chain alkyl groups, branched chain alkyl groups and alkyl
phenoxypoly(ethyleneoxy) ethanol, R.sub.18 containing no more than 21
carbon atoms.
15. A binder according to claim 11 wherein the non-ionic organic compound
is styrene.
16. A binder according to claim 11 wherein the non-ionic organic compound
is butyl acrylate.
17. A binder according to claim 11 wherein the non-ionic organic compound
is 2-ethylhexyl acrylate.
18. A binder according to claim 11 wherein R.sub.5, R.sub.6 and R.sub.7 are
independently selected from the group consisting of hydrogen,
unsubstituted cycloalkyl, unsubstituted straight chain alkyl groups
containing no more than 7 carbon atoms, unsubstituted branched chain alkyl
groups containing no more than 7 carbon atoms, cyano, cyanoalkyl and the
radical
##STR15##
wherein R.sub.19 is hydrogen or an organic radical containing no more than
10 carbon atoms.
19. A binder according to claim 11 wherein R.sub.5, R.sub.6 and R.sub.7 are
independently selected from the group consisting of hydrogen,
unsubstituted straight chain alkyl groups containing no more than 5 carbon
atoms, unsubstituted branched chain alkyl groups containing no more than 5
carbon atoms, and the radical
##STR16##
wherein R.sub.19 is hydrogen or an organic radical containing no more than
10 carbon atoms; and X is a covalent bond or a member selected from the
group consisting of unsubstituted cycloalkyl groups, unsubstituted
straight chain alkyl groups containing no more than 6 carbon atoms, and
unsubstituted branched chain alkyl groups containing no more than 6 carbon
atoms.
20. A binder according to claim 11 wherein X is an unsubstituted straight
chain alkyl group.
21. A binder according to claim 11 wherein R.sub.5, R.sub.6 and R.sub.7 are
independently selected from the group consisting of hydrogen, methyl,
ethyl, carboxylate, methyl substituted with carboxylate and ethyl
substituted with carboxylate, only one of R.sub.5, R.sub.6 and R.sub.7
comprising a carboxylate group; R.sub.8 selected from the group consisting
of hydrogen, unsubstituted cycloalkyl and unsubstituted alkyl; and X is a
covalent bond.
22. A binder according to claim 21 wherein R.sub.5 and R.sub.6 combined
contain no more than 9 carbon atoms; and R.sub.8 and R.sub.19 contain no
more than 7 carbon atoms.
23. A binder according to claim 11 wherein R.sub.5 and R.sub.6 combined
contain no more than 4 carbon atoms; R.sub.7 and X combined contain no
more than 3 carbon atoms, at least one of R.sub.5, R.sub.6 and R.sub.7 is
carboxy or carboxyalkyl and R.sub.8 is hydrogen.
24. A binder according to claim 11 wherein the carboxylate group containing
organic compound is a monoolefinically unsaturated diacid.
25. A binder according to claim 24 wherein said diacid is itaconic acid.
26. A binder according to claim 24 wherein said diacid is maleic acid.
27. A binder according to claim 11 wherein the carboxylate group containing
organic compound is a C.sub.1 to C.sub.5 semi-ester of a monoolefinically
unsaturated diacid.
28. A binder according to claim 11 wherein R.sub.9, R.sub.10 and R.sub.11
do not contain hydroxyl groups and R.sub.9, R.sub.10, R.sub.11 and
R.sub.12 do not contain carboxylate groups.
29. A binder according to claim 11 wherein R.sub.9, R.sub.10 and R.sub.11
are independently selected from the group consisting of hydrogen,
unsubstituted cycloalkyl, unsubstituted straight chain alkyl containing no
more than 7 carbon atoms, and unsubstituted branched chain alkyl
containing no more than 7 carbon atoms.
30. A binder according to claim 11 wherein R.sub.9, R.sub.10 and R.sub.11
are independently selected from the group consisting of hydrogen,
unsubstituted straight chain alkyl containing no more than 5 carbon atoms
and unsubstituted branched chain alkyl containing no more than 5 carbon
atoms.
31. A binder according to claim 11 wherein R.sub.9, R.sub.10 and R.sub.11
are independently selected from the group consisting of hydrogen, methyl
and ethyl.
32. A binder according to claim 11 wherein R.sub.12 is a member selected
from the group consisting of alkyl substituted with a hydroxyl group at
least 2 carbon atoms away from the carboxylate group, and cycloalkyl
substituted with a hydroxyl group at least 2 carbon atoms away from the
carboxylate group.
33. A binder according to claim 11 wherein Y is a member selected from the
group consisting of straight chain alkyl containing no more than 6 carbon
atoms, branched chain alkyl containing no more than 6 carbon atoms, and
cycloalkyl containing no more than 6 carbon atoms.
34. A binder according to claim 11 wherein Y is a straight chain alkyl
containing no more than 6 carbon atoms.
35. A binder according to claim 11 wherein Y is a covalent bond.
36. A binder according to claim 11 wherein the hydroxy ester is a member
selected from the group consisting of hydroxy alkyl esters of acrylic
acid, hydroxy cycloalkyl esters of acrylic acid, hydroxy alkyl esters of
methacrylic acid, and hydroxy cycloalkyl esters of methacrylic acid, the
hydroxy ester containing from 5 to 9 carbon atoms.
37. A binder according to claim 11 wherein the hydroxy ester is
2-hydroxyethyl acrylate.
38. A binder according to claim 11 wherein the hydroxy ester is
hydroxypropyl methacrylate.
39. A binder according to claim 11 wherein R.sub.13, R.sub.14 and R.sub.15
contain no carboxylate groups.
40. A binder according to claim 11 wherein R.sub.13, R.sub.14 and R.sub.15
are selected from the group consisting of hydrogen, unsubstituted
cycloalkyl containing no more than 7 carbon atoms, unsubstituted straight
chain alkyl containing no more than 7 carbon atoms, and unsubstituted
branched chain alkyl containing no more than 7 carbon atoms; R.sub.16 and
R.sub.17 are selected from the group consisting of hydrogen, unsubstituted
cycloalkyl containing no more than 6 carbon atoms, unsubstituted straight
chain alkyl containing no more than 6 carbon atoms, and unsubstituted
branched chain alkyl containing no more than 6 carbon atoms, at least one
of R.sub.16 and R.sub.17 being hydrogen; and Z is a member selected from
the group consisting of a covalent bond, unsubstituted cycloalkyl
containing no more than 6 carbon atoms, unsubstituted straight chain alkyl
containing no more than 6 carbon atoms and unsubstituted branched chain
alkyl containing no more than 6 carbon atoms.
41. A binder according to claim 11 wherein R.sub.13, R.sub.14 and R.sub.15
are independently selected from the group consisting of hydrogen,
unsubstituted straight chain alkyl containing no more than 5 carbon atoms,
and unsubstituted branched chain alkyl containing no more than 5 carbon
atoms; and Z is a covalent bond or a straight chain alkyl containing no
more than 6 carbon atoms.
42. A binder according to claim 11 wherein R.sub.13, R.sub.14 and R.sub.15
are independently selected from the group consisting of hydrogen, methyl
and ethyl.
43. A binder according to claim 11 wherein Z is a covalent bond.
44. A binder according to claim 11 wherein R.sub.13, R.sub.14 and R.sub.16
are hydrogen, R.sub.15 is hydrogen or methyl, R.sub.17 is hydrogen, methyl
or ethyl, and Z is a covalent bond.
45. A binder according to claim 11 wherein the amide is acrylamide.
46. A binder according to claim 11 wherein said mixture of comonomers
comprises a member selected from the group consisting of butyl acrylate
and 2-ethylhexyl acrylate, a member selected from the group consisting of
maleic acid and itaconic acid, and a member selected from the group
consisting of 2-hydroxyethyl acrylate and hydroxypropyl methacrylate.
47. A binder according to claim 11 wherein said mixture of comonomers
comprises a member selected from the group consisting of butyl acrylate
and 2-ethylhexyl acrylate, a member selected from the group consisting of
maleic acid and itaconic acid, a member selected from the group consisting
of 2-hydroxyethyl acrylate and hydroxypropyl methacrylate, and acrylamide.
48. A binder according to claim 11 wherein the styrene-butadiene copolymer
latex comprises a carboxylated styrene-butadiene copolymer latex.
49. A binder according to claim 11 wherein said latex is formulated with
between about 0.5 percent and about 15 percent, by weight, of a
substantially non-formaldehyde emitting reactive monomer.
50. A binder according to claim 49 wherein said substantially
non-formaldehyde emitting reactive monomer comprises
methylacryloamidoglycolate methyl ether.
51. A binder according to claim 1 wherein said aqueous dispersion of
discrete particles of highly functionalized emulsion copolymer is admixed,
in an amount of about 2 percent to about 30 percent, by weight, with a
latex.
52. A binder according to claim 11 wherein said aqueous dispersion of
discrete particles of highly functionalized emulsion copolymer is admixed,
in an amount of about 2 percent to about 30 percent, by weight, with a
latex.
53. A binder according to claim 11 wherein said aqueous dispersion of
discrete particles of highly functionalized emulsion copolymer is admixed,
in an amount of about 3 percent to about 15 percent, by weight, with a
latex.
54. A binder according to claim 11 wherein said aqueous dispersion of
discrete particles of highly functionalized emulsion copolymer is admixed,
in an amount of about 5 percent to about 12 percent, by weight, with a
latex.
55. A binder according to claim 11 wherein said mixture of comonomers
comprises a member selected from the group consisting of styrene, butyl
acrylate and 2-ethylhexyl acrylate, a member selected from the group
consisting of maleic acid and itaconic acid, and a member selected from
the group consisting of 2-hydroxyethyl acrylate and hydroxypropyl
methacrylate.
56. A binder according to claim 11 wherein said mixture of comonomers
comprises a member selected from the group consisting of maleic acid and
itaconic acid, and acrylamide.
57. A fast curing binder for nonwoven cellulosic materials, said binder
comprising an aqueous dispersion of discrete particles of a highly
functionalized emulsion copolymer formed by the copolymerization of a
mixture of comonomers comprising;
(1) one or more water insoluble polymerizable olefinically unsaturated
non-ionic organic compounds;
(2) one or more water soluble olefinically unsaturated organic compounds
having at least one carboxylate group therein; and
(3) one or more water soluble olefinically unsaturated carboxylic acid
hydroxy esters; said aqueous dispersion of discrete particles of highly
functionalized emulsion copolymer being admixed with a latex selected from
the group consisting of styrene-butadiene resin (SBR) copolymer latexes,
vinyl acetate/acrylate copolymer latexes, and all-acrylate copolymer
latexes.
58. A fast curing binder for nonwoven cellulosic materials, said binder
comprising an aqueous dispersion of discrete particles of a highly
functionalized emulsion copolymer formed by the copolymerization of a
mixture of comonomers comprising;
(1) one or more water insoluble polymerizable olefinically unsaturated
non-ionic organic compounds;
(2) one or more water soluble olefinically unsaturated organic compounds
having at least one carboxylate group therein; and
(3) one or more water soluble olefinically unsaturated amides;
said aqueous dispersion of discrete particles of highly functionalized
emulsion copolymer being admixed with a latex selected from the group
consisting of styrene-butadiene resin (SBR) copolymer latexes, vinyl
acetate/acrylate copolymer latexes, and all-acrylate copolymer latexes.
59. A fast-curing binder for nonwoven cellulosic materials, said binder
comprising an aqueous dispersion of discrete particles of a highly
functionalized emulsion copolymer formed by the copolymerization of a
mixture of comonomers comprising:
(1) one or more water insoluble polymerizable olefinically unsaturated
non-ionic organic compounds having the general formula:
##STR17##
wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected
from hydrogen, halogen, nitro, amino and organic radicals;
(2) one or more water soluble olefinically unsaturated organic compounds
having at least one carboxylate group, said compounds having the general
formula:
##STR18##
wherein R.sub.5, R.sub.6, and R.sub.7 are independently selected from
hydrogen, halogen, nitro, amino, and organic radicals; R.sub.8 is hydrogen
or an organic radical; and X is an organic radical or a covalent bond; and
(3) one or more water soluble olefinically unsaturated carboxylic acid
hydroxy esters of the general formula:
##STR19##
wherein R.sub.9, R.sub.10 and R.sub.11 are independently selected from
hydrogen, halogen, nitro, amino, and organic radicals; and R.sub.12 is an
organic radical having at least 2 carbon atoms, with at least one of
R.sub.9 R.sub.10, R.sub.11 and R.sub.12 being an organic radical
containing a hydroxyl substituent, said hydroxyl substituent being located
on a carbon atom which is at least 2 carbon atoms away from the
carboxylate group; and Y is an organic radical or a covalent bond; said
aqueous dispersion of discrete particles of highly functionalized emulsion
copolymer being admixed with a latex to produce said binder, the latex
being selected from the group consisting of styrene-butadiene resin (SBR)
copolymer latexes, vinyl acetate/acrylate copolymer latexes, and
all-acrylate copolymer latexes.
60. A fast-curing binder for nonwoven cellulosic materials, said binder
comprising an aqueous dispersion of discrete particles of a highly
functionalized emulsion copolymer formed by the copolymerization of a
mixture of comonomers comprising:
(1) one or more water insoluble polymerizable olefinically unsaturated
non-ionic organic compounds having the general formula:
##STR20##
wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected
from hydrogen, halogen, nitro, amino and organic radicals;
(2) one or more water soluble olefinically unsaturated organic compounds
having at least one carboxylate group, said compounds having the general
formula:
##STR21##
wherein R.sub.5, R.sub.6, and R.sub.7 are independently selected from
hydrogen, halogen, nitro, amino, and organic radicals; R.sub.8 is hydrogen
or an organic radical; and X is an organic radical or a covalent bond; and
(3) one or more water soluble olefinically unsaturated amides having the
general formula:
##STR22##
wherein R.sub.13, R.sub.14 and R.sub.15 are independently selected from
hydrogen, halogen, nitro, amino, and organic radicals; R.sub.16 and
R.sub.17 are hydrogen or organic radicals; and Z is an organic radical or
a covalent bond;
said aqueous dispersion of discrete particles of highly functionalized
emulsion copolymer being admixed with a latex to produce said binder, the
latex being selected from the group consisting of styrene-butadiene resin
(SBR) copolymer latexes, vinyl acetate/acrylate copolymer latexes, and
all-acrylate copolymer latexes.
61. A fast-curing binder for nonwoven cellulosic materials, said binder
comprising an aqueous dispersion of discrete particles of a highly
functionalized emulsion copolymer formed by the copolymerization of a
mixture of comonomers comprising:
and 10 phm to about 60 phm of one or more water insoluble polymerizable
olefinically unsaturated non-ionic organic compounds;
the balance of said mixture of comonomers comprising a mixture of
(a) one or more water soluble olefinically unsaturated organic compounds
having at least one carboxylate group therein; and
(b) one or more water soluble olefinically unsaturated carboxylic acid
hydroxy esters or one or more water soluble olefinically unsaturated
amides or a mixture thereof;
said aqueous dispersion of discrete particles of highly functionalized
emulsion copolymer being admixed with a latex to produce said binder, the
latex being selected from the group consisting of styrene-butadiene resin
(SBR) copolymer latexes, vinyl acetate/acrylate copolymer latexes, and
all-acrylate copolymer latexes.
62. A binder according to claim 61 wherein said balance of said mixture of
comonomers comprises a mixture of substantially equal quantities of the
carboxylate group containing compound, the hydroxy ester, if present, and
the amide, if present.
63. A binder according to claim 61 wherein said one or more non-ionic
organic compounds is present in a quantity of about 20 phm to about 50
phm.
64. A binder according to claim 61 wherein said one or more non-ionic
organic compounds is present in a quantity of about 30 phm to about 40
phm.
Description
FIELD OF THE INVENTION
This invention relates to polymeric binders for cellulose and more
particularly to fast curing compositions based on a low viscosity highly
functionalized emulsion copolymer admixed with a polymeric latex, which is
especially useful where low formaldehyde emitting applications are
involved.
BACKGROUND OF THE INVENTION
During the past few years there has been a substantial growth in the
production of high-strength paper and cloth products having a nonwoven,
randomly-oriented structure, bonded with a polymeric resin binder. Such
products are finding wide use as high-strength, high-absorbency materials
for disposable items such as consumer and industrial wipes or towels,
diapers, surgical packs and gowns, industrial work clothing and feminine
hygiene products. They are also used for durable products such as carpet
and rug backings, apparel interlinings, automotive components and home
furnishings, and for civil engineering materials such as road underlays.
There are several ways to apply a binder to these materials, including
spraying, print binding, and foam application. Further, depending on the
end use, various ingredients such as catalysts, cross-linkers,
surfactants, thickeners, dyes, and flame retardant salts may also be
incorporated into the binder.
In the high-speed, high-volume manufacture of cellulosic products such as
wet wipes, an important binder property is a fast cure rate; i.e., the
finished product must reach substantially full tensile strength in a very
short time after binder application so that production rates are not
unduly slowed down. In these products, such a property is usually obtained
by using a binder which is either self cross-linkable or by incorporating
an external cross-linker into the binder formulation. When this is done,
the cross-linker apparently not only interacts with the binder monomers
but with the hydroxyl groups on the cellulose fibers to quickly form very
strong bonds.
At present, there are a number of available binder formulations which meet
this requirement. However, these materials are typified by incorporating
one or more constituents which, over some period of time, will emit
formaldehyde in amounts which may be sufficient to cause skin and
respiratory irritation in many people, particularly children. Most
recently, several of the leading manufacturers of nonwoven cellulosic
products have expressed a desire to replace such binders with products
offering equivalent levels of performance in cellulose but without the
emission of formaldehyde. Although a number of ostensibly "zero"
formaldehyde or "0 CH.sub.2 O" cellulose binders have been proposed, they
have either not been truly "0" in formaldehyde content or have not shown
sufficiently fast cure rates to be acceptable in high-volume production
applications.
One approach to a fast curing, "zero" formaldehyde binder for nonwoven
cellulosic materials utilizes a binder comprising a solution copolymer
formed by reacting a mixture of two or more water soluble olefinically
unsaturated organic comonomers. The solution copolymer is admixed with a
non-formaldehyde emitting latex to produce a final composition which is
essentially free of formaldehyde and which, when cured on nonwoven
cellulosic material, will achieve about 80 percent of fully cured wet
tensile strength in 8 seconds or less.
While this approach results in providing zero formaldehyde emitting binders
which are capable of fast curing, solution copolymers raise the viscosity
and cause thickening of the binders in which they are incorporated. In
certain applications, it is necessary to maintain the viscosity of the
binder at a relatively low level in order to assure adequate penetration
of the binder into the nonwoven substrate.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the present invention, a low viscosity, fast curing,
"zero" formaldehyde binder for nonwoven cellulosic materials is provided.
The binder comprises an aqueous dispersion of discrete particles of a
highly functionalized emulsion copolymer formed by reacting a mixture of
comonomers comprising (1) one or more water insoluble polymerizable
olefinically unsaturated non-ionic organic compounds; (2) one or more
water soluble olefinically unsaturated organic compounds having at least
one carboxylate group therein; and (3) one or more water soluble
olefinically unsaturated carboxylic acid hydroxy esters or water soluble
olefinically unsaturated amides, or a mixture thereof; the mixture of
comonomers usually being dispersed by means of a suitable surfactant. The
binder also preferably comprises a non-formaldehyde emitting latex which
is admixed with the aqueous copolymer dispersion to produce a final
composition which is essentially free of formaldehyde, which, when cured
on nonwoven cellulosic material, will achieve about 80 percent of fully
cured wet tensile strength in 8 seconds or less, and which has a viscosity
of less than about 600 cps at 30 percent solids content at a pH value of
up to about pH 6 and a viscosity of less than about 1200 cps at 35 percent
solids content at a pH value of up to about pH 6.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises a low viscosity, fast curing, zero
formaldehyde binder composition for nonwoven cellulosic materials. The
binder comprises a polymeric composition formed by the emulsion
polymerization of a mixture containing at least one water insoluble
monomer and at least two water soluble monomers.
The water insoluble monomer comprises one or more water insoluble non-ionic
organic compounds having at least one olefinically unsaturated linkage,
said compounds having the general formula:
##STR1##
wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently hydrogen,
halogen, nitro, amino, and organic radicals. Normally, the number of all
the carbon atoms in compound (a) is no greater than 30.
The first of the water soluble comonomers, all of which are highly
functionalized organic compounds, comprises one or more water soluble
organic compounds having at least one olefinically unsaturated linkage
with at least one carboxylate group, said compounds having the general
formula:
##STR2##
wherein R.sub.5, R.sub.6 and R.sub.7 are independently hydrogen, halogen,
nitro, amino, and organic radicals; R.sub.8 is hydrogen or an organic
radical, usually containing no more than about 10 carbon atoms; and X is a
covalent bond or an organic radical, usually of no more than about 10
carbon atoms. Normally, the number of all the carbon atoms in compound (b)
is no greater than 30.
The other water soluble comonomers are either water soluble hydroxy esters
or water soluble amides.
The hydroxy ester comonomers comprise one or more water soluble compounds
having the general formula:
##STR3##
wherein R.sub.9, R.sub.10 and R.sub.11 are independently selected from
hydrogen, halogen, nitro, amino, and organic radicals, usually of no more
than 10 carbon atoms; R.sub.12 is an organic radical having at least 2,
and usually no more than 10, carbon atoms, with at least one of R.sub.9,
R.sub.10, R.sub.11 , and R.sub.12 being an organic radical having a
hydroxyl substituent thereon, said hydroxyl substituent being at least 2
carbon atoms away from the carboxylate group. Where one or more of
R.sub.9, R.sub.10, and R.sub.11 are organic radicals having a hydroxyl
substituent, R.sub.12 is preferably an unsubstituted hydrocarbyl radical,
usually of no more than 10 carbon atoms. Y is a covalent bond or an
organic radical, usually of no more than about 10 carbon atoms.
The amide comonomers comprise one or more water soluble compounds having
the general formula:
##STR4##
wherein R.sub.13, R.sub.14, and R.sub.15 are independently selected from
nitro, hydrogen, halogen, amino, and organic radicals; R.sub.16 and
R.sub.17 are hydrogen or organic radicals having no more than 6 carbon
atoms; and Z is a covalent bond or an organic radical, usually of no more
than about 10 carbon atoms.
The term "organic" radical, when used herein, broadly refers to any
carbon-containing radical. Such radicals may be cyclic or acyclic, may
have straight or branched chains, and can contain one or more hetero atoms
such as sulfur, nitrogen, oxygen, phosphorus, and the like. Further, they
may be substituted with one or more substituents such as thio, hydroxy,
nitro, amino, cyano, carboxyl and halogen. In addition to aliphatic
chains, such radicals may contain aryl groups, including arylalkyl and
alkylaryl groups, and cycloalkyl groups, including alkyl-substituted
cycloalkyl and cycloalkyl-substituted alkyl groups, with such groups, if
desired, being substituted with any of the substituents listed herein
above. When cyclic groups are present, whether aromatic or nonaromatic, it
is preferred that they have only one ring. Preferred organic radicals for
compounds (b), (c), and (d) are, in general, free of olefinic and alkynyl
linkages.
The term "water soluble" shall denote a solubility in an amount of at least
1 g/100 ml. measured at a temperature of 20.degree. C. in deionized water.
Preferably, the water soluble comonomers are soluble in water to the
extent of at least 5 g/100 ml. The water insoluble monomers preferably are
soluble to the extent of no more than about 0.7 9/100 ml. A solubility of
no more than about 0.2 g/100 ml. is especially preferred.
In compound (a), it is further preferred that R.sub.1, R.sub.2 and R.sub.3
be hydrogen, aryl, alkylaryl, arylalkyl, cycloalkyl or straight or
branched chain alkyl groups which have no more than 10 carbon atoms and
that R.sub.4 be hydrogen, aryl, alkylaryl, arylalkyl, cycloalkyl or
straight or branched alkyl groups which have no more than 10 carbon atoms
or
##STR5##
wherein R.sub.18 is aryl, alkylaryl, arylalkyl, cycloalkyl, or straight or
branched chain alkyl or polyalkylene ether having no more than 21 carbon
atoms. In a more preferred form, compound (a) is a styrene derivative
wherein R.sub.1 and R.sub.2 are hydrogen, R.sub.3 is hydrogen or methyl
and R.sub.4 is phenyl or substituted phenyl or an ester of acrylic or
methacrylic acid wherein R.sub.1 and R.sub.2 are hydrogen, R.sub.3 is
hydrogen or methyl and R.sub.4 is
##STR6##
wherein R.sub.18 is a straight or branched chain alkyl or polyalkylene
ether group having no more than 21 carbon atoms. In the most preferred
form of all, compound (a) is styrene, butyl acrylate, or 2-ethylhexyl
acrylate. Compound (a) can also be an ester formed by reacting acrylic
acid with an alkyl phenoxypoly(ethyleneoxy)ethanol such as IGEPAL CO-420,
IGEPAL CA-430, IGEPAL CO-420 or IGEPAL CO-430, available from GAF
Corporation, New York, N.Y.
In compound (b), it is further preferred that R.sub.5, R.sub.6, and R.sub.7
be hydrogen or unsubstituted cycloalkyl or unsubstituted, straight or
branched chain alkyl groups which have no more than 7 carbon atoms, with
the exception that at least one of R.sub.5, R.sub.6, and R.sub.7 may be a
nitrile or bear a cyano group or be or bear a carboxylate group
##STR7##
wherein R.sub.19 is hydrogen or an organic radical, usually having no more
than about 10 carbon atoms. More preferably, R.sub.5, R.sub.6, and
R.sub.7, except for the group being the nitrile or carboxylate group or
bearing the cyano or carboxylate group are hydrogen or unsubstituted,
straight or branched chain alkyl groups having no more than 5 carbon
atoms. When X is an organic radical, it preferably has no more than 6
carbon atoms and is an unsubstituted, branched or unbranched alkyl or
unsubstituted cycloalkyl radical and when an alkyl group, is most
preferably unbranched.
In the most preferred form of all, compound (b) is a dicarboxylic acid,
wherein R.sub.5, R.sub.6, and R.sub.7 are all independently hydrogen,
carboxylate groups, or ethyl or methyl groups, either unsubstituted or
substituted with a carboxylate group, provided that R.sub.5, R.sub.6 and
R.sub.7 comprise, in total, only one carboxylate group. Most preferred for
R.sub.8 and R.sub.19 are hydrogen and unsubstituted alkyl or unsubstituted
cycloalkyl groups, provided at least one of R.sub.8 and R.sub.19 is
hydrogen. Most preferred for X is a covalent bond.
In particular regard to the most preferred embodiment of compound (b), it
is still more preferred that, except for the carboxylate groups, the
remainder of the compound be unsubstituted; i.e., consist of only carbon
and hydrogen atoms, and that the maximum number of carbon atoms in the
compound be 30; with R.sub.5 and R.sub.6 combined having no more than 9;
with R.sub.8 and R.sub.19 having no more than 7 carbon atoms, provided
that at least one of R.sub.8 and R.sub.19 is hydrogen. In the very most
preferred embodiment, each side of the olefinic linkage has no more than
about 5 carbon atoms and at least one of R.sub.5, R.sub.6, and R.sub.7 is
or contains the carboxylate group
##STR8##
and both of R.sub.8 and R.sub.19 are hydrogen.
Suitable polymerizable, water-soluble monomers for compound (b) according
to the above most preferred description include monoolefinically
unsaturated diacids, such as tetrahydrophthalic acid, methylenesuccinic
acid (itaconic acid), the cis- and trans- forms of butenedioic acid
(maleic and fumaric acids), and both the cis- and trans- forms (where such
exist) of the diacids resulting when one or more of the hydrogen atoms on
the carbon chains of maleic/fumaric acid or itaconic acid is replaced with
a methyl or ethyl group, as well as the C.sub.1 to C.sub.10 and,
preferably, C.sub.1 to C.sub.5 semi-esters of these acids. Of these,
itaconic acid and maleic acid are most preferred.
For compound (c), it is preferred that R.sub.9, R.sub.10, and R.sub.11 be
free of hydroxyl and carboxylate substituents and, even more preferably,
that they be hydrogen or unsubstituted cycloalkyl or unsubstituted,
straight or branched chain alkyl groups which have no more than 7 carbon
atoms. Most preferably, R.sub.9, R.sub.10, and R.sub.11 are hydrogen or
unsubstituted, straight or branched chain alkyl groups having no more than
5 carbon atoms. In the very most preferred form of all, R.sub.9, R.sub.10,
and R.sub.11 are all independently ethyl, methyl, or hydrogen. R.sub.12 is
also preferably free of carboxylate groups and is most preferably an alkyl
or cycloalkyl group, substituted at least 2 carbon atoms away from the
carboxylate group with a hydroxyl group. When Y is an organic radical, it
is preferably a branched or unbranched, unsubstituted alkyl or
unsubstituted cycloalkyl group with no more than about 6 carbon atoms and,
when an alkyl group, is preferably unbranched. However, most preferred for
Y is a covalent bond.
Preferred polymerizable, water-soluble, unsaturated compounds according to
the above most preferred description for compound (c) are the hydroxy
alkyl and hydroxy cycloalkyl esters of acrylic and methacrylic acids, and
while the esterifying moiety must have at least 2 carbon atoms, it
preferably has no more than about 6, and, more preferably, no more than
about 4 carbon atoms. Of the hydroxy alkyl and hydroxy cycloalkyl esters
of acrylic and methacrylic acids meeting these criteria, 2-hydroxyethyl
acrylate and hydroxypropyl methacrylate are most preferred.
For compound (d)), it is preferred that R.sub.13, R.sub.14, and R.sub.15 be
free of carboxylate substituents and, even more preferably, that they be
hydrogen or unsubstituted cycloalkyl or unsubstituted, straight or
branched chain alkyl groups which have no more than 7 carbon atoms. Most
preferably, R.sub.13, R.sub.14, and R.sub.15 are hydrogen or straight or
branched chain, unsubstituted alkyl groups having no more than 5 carbon
atoms. In the very most preferred form of all, R.sub.13, R.sub.14, and
R.sub.15 are all independently ethyl, methyl, or hydrogen. Preferred for
R.sub.16 and R.sub.17 are hydrogen or unsubstituted, branched or
unbranched alkyl or unsubstituted cycloalkyl groups each having no more
than 6 carbon atoms, provided that at least one of R.sub.16 and R.sub.17
is hydrogen. When Z is an organic radical, it is preferably an
unsubstituted, branched or unbranched alkyl or cycloalkyl group with no
more than about 6 carbon atoms and, when an alkyl group, is more
preferably unbranched. However, most preferred for Z is a covalent bond.
Preferred polymerizable water-soluble, unsaturated compounds according to
the above most preferred description for formula (d) are the primary and
secondary amides of acrylic and methacrylic acid, with R.sub.16 being
hydrogen and R.sub.17 being either hydrogen, methyl, or ethyl. Of the
amides meeting these criteria, acrylamide is most preferred.
The copolymerization reaction is conducted with between about 10 parts and
about 60 parts of compound (a) per hundred parts total monomer (phm), the
balance being comprised of compounds (b) and (c), compounds (b) and (d) or
compounds (b), (c) and (d). In a preferred embodiment of the present
invention, the comonomeric mixture preferably comprises between about 20
and about 50 phm but, more preferably, between about 30 and about 40 phm
of compound (a). The preferred dicarboxylic acid monomers of compound (b),
the preferred hydroxy ester monomers of compound (c), when present, and
the preferred amide monomers of compound (d), when present, are preferably
present in substantially equal quantities.
Suitable copolymers of the above described comonomers can be prepared by
free-radical initiated emulsion polymerization methods, using either
thermal or redox techniques. Further, the reaction may be conducted by
batch, semi-batch or continuous procedures, which are well known for use
in conventional polymerization reactions. Free-radical polymerization
involves emulsifying the ingredients in water by gradually adding the
monomers to be polymerized and a suitable surfactant or surfactants
simultaneously to an aqueous reaction medium with agitation at rates
proportionate to the respective percentage of each monomer in the finished
copolymer and initiating and continuing the polymerization with a suitable
reaction catalyst. Optionally, one or more of the comonomers and
surfactant(s) can be added disproportionately throughout the
polymerization so that the polymer formed during the initial stages of
polymerization will have a composition and/or a molecular weight differing
from that formed during the intermediate and later stages of the same
polymerization reaction.
The purpose of the surfactant is to initiate particle formation and to
provide physical stability of the dispersion. Illustrative of anionic
surfactants, which are preferred, are alkali metal or ammonium salts of
alkyl, aryl, or alkylaryl sulfonates, sulfates, phosphates, phosphonates,
etc. Examples include sodium lauryl sulfate, sodium octylphenol glycol
ether sulfate, sodium dodecylbenzene sulfonate, sodium lauryl diglycol
sulfate, ammonium tritertiarybutylphenol penta- and octa-glycol sulfates,
dioctyl sodium sulfosuccinate, alpha-olefin sulfonates and sulfonated
biphenyl ethers. Numerous other examples of suitable surfactants are
disclosed, for example, in U.S. Pat. No. 2,600,831, the disclosure of
which is incorporated herein by reference in its entirety.
Illustrative water soluble, free-radical initiators are hydrogen peroxide,
sodium persulfate, potassium persulfate and ammonium persulfate, and
combinations of the above with a reducing agent activator, such as a
sulfite, more specifically an alkali metabisulfite, hyposulfite or
hydrosulfite, glucose, ascorbic acid, erythorbic acid, etc. to form a
"redox" system. Normally the amount of initiator used ranges from about
0.1 percent to about 5 percent, by weight, based on the monomer charge. In
a redox system, a corresponding range (about 0.1 to about 5 percent) of
reducing agent is also normally used.
The reaction, once started, is continued, with agitation, at a temperature
sufficient to maintain an adequate reaction rate until most, or all, of
the comonomers are consumed and until the reaction medium reaches a
polymer solids concentration between about 1 percent and about 50 percent,
by weight. Normally, the solids content will be kept above 10 percent to
minimize drying problems when the binder is applied to cellulosic
materials.
At this point, the reaction product will typically comprise an aqueous
dispersion of discrete particles of a very highly functionalized emulsion
copolymer, i.e. an emulsion polymer characterized by having a multiplicity
of hydrophilic functional groups pendant from the polymer backbone. The
dispersed particles will have a size range of about 100 nm to about 2100
nm as measured by a Coulter Model N-4 Submicron Particle Size Analyzer.
The dispersion, which is milky white in appearance, normally will have a
Brookfield viscosity in the range of about 5 cps to about 100 cps.
In the present invention, reaction temperatures in the range of about
10.degree. C. to about 100.degree. C. will yield satisfactory polymeric
compositions. When persulfate systems are used, the temperature of the
dispersion is normally in the range of about 60.degree. C. to about
100.degree. C., while, in redox systems, the temperature is normally in
the range of about 10.degree. C. to about 70.degree. C., and preferably
about 30.degree. C. to about 60.degree. C.
The binder composition of the present invention is formed when the aqueous
dispersion of discrete particles of highly functionalized emulsion
copolymer described above, in an amount of about 2 percent to about 30
percent, by weight, more preferably about 3 percent to about 15 percent
and most preferably about 5 percent to about 12 percent, is admixed with a
fast-curing polymeric latex.
A number of commercially available latexes can be used with the aqueous
dispersion of discrete particles of highly functionalized emulsion
copolymer in accordance with the present invention. These include
styrene-butadiene resin (SBR) copolymers containing between about 50
percent and about 70 percent styrene, carboxylated SBR copolymers (i.e.,
an SBR composition in which between about 0.2 percent and about 10 percent
of one or more ethylenically unsaturated mono- or dicarboxylic acid
monomers, such as acrylic acid, methacrylic acid, itaconic acid, maleic
acid or fumaric acid, is copolymerized therewith), vinyl acetate/acrylate
copolymers (which may also have up to about 5 percent of one or more
ethylenically unsaturated mono- or dicarboxylic acid monomers added
thereto) and all-acrylate copolymer latexes.
Several rheological properties of water base latexes, such as those
described above, are of particular importance when they are to be applied
to the formulation of binders for cellulosic materials. For example, in
many cases, control of latex particle size and particle size distribution
is critical to the realization of desirable physical properties in the
finished latex. Further, control of latex viscosity is an important factor
due to its influence on polymer distribution, filler loading, and fiber
wetting. While all of the polymer systems listed above may be polymerized
using conventional emulsion polymerization techniques, this is frequently
done in the presence of an added seed polymer to optimize these factors.
In addition, while such latexes may have either a unimodal or polymodal
particle size distribution, they are typically unimodal with a particle
size in the range between about 100 nm and about 400 nm and a viscosity in
the range between about 20 cps and about 2000 cps, at a solids content in
the range of about 25 percent to about 65 percent.
In order to impart the fast-curing properties needed for cellulose binder
compositions, the latexes may be formulated with an amount of a
cross-linker or other reactive monomer being added during the formulation
thereof. The most effective prior art cross-linkers commonly used with
these latexes are known formaldehyde emitters. Methoxymethyl melamine, for
example, is used as a post-added cross-linker. N-methylolacrylamide,
isobutoxylethyl acrylamide (IBMA) and glyoxal bisacrylamide are used as
copolymerizable cross-linkers.
However, it has been found that in the production of these latexes, the
formaldehyde emitting cross-linking materials can be entirely replaced
with between about 0.5 percent and about 15 percent, by weight, of one or
more low or non-formaldehyde emitting, polymerizable reactive monomers
such as methyl acryloamidoglycolate methyl ether (MAGME). MAGME has been
found to be especially effective in producing fast-curing, "zero"
formaldehyde latexes. As used herein, the terms "non-formaldehyde" and
"`zero` formaldehyde," when used in relation to the binders of the present
invention, shall be taken to mean that a free formaldehyde level of 10 ppm
or less is observed in the fully cured compositions. Such a level is close
to the minimum level of detectability for most analytical methods and well
below the level known to cause respiratory and skin irritation problems in
people. The term "fully-cured" shall mean the wet tensile strength
observed after curing for 180 seconds at 149.degree. C.
After admixing one of the above described "zero" formaldehyde latexes with
the aqueous dispersion of discrete particles of highly functionalized
emulsion copolymer, the admixture is diluted with sufficient deionized
water to produce a total nonvolatile solids content between about 5
percent and about 40 percent and preferably between about 20 percent and
about 35 percent. Depending on the particular application involved, other
solids contents may be equally effective. When cured at about 190.degree.
C. for between about 4 seconds and about 8 seconds on a nonwoven
cellulosic material, such binder compositions usually will have wet
tensile strengths which are as much as 50 percent higher than those
obtainable with the basic latex alone.
It is an advantage of the present invention that wet tensile strengths
greater than are obtained with commercially available "zero" formaldehyde
latexes can be realized by using the aqueous dispersion of discrete
particles of highly functionalized emulsion copolymers of the present
invention. Wet tensile strengths of up to about 80 percent of the wet
tensile strengths of commercially available formaldehyde emitting latexes
can be realized. A particular advantage is that the aqueous dispersions of
this invention display desirable wet strength enhancement without
producing a high viscosity binder composition as is the case with the
previously mentioned solution polymers. For example, whereas a binder
prepared from 95 parts of a "zero" formaldehyde styrene-butadiene latex
and 5 parts of a solution polymer comprising copolymerized equal parts of
itaconic acid, hydroxyethyl acrylate and acrylamide had viscosities in the
range of 700 to 1800 cps at 30 percent total solids at pH 6 and over 2000
cps at 35 percent total solids content at pH 6, a binder prepared from 95
parts of a "zero" formaldehyde styrene-butadiene latex and 5 parts of an
aqueous dispersion comprising a copolymerized mixture of 40 parts of butyl
acrylate, 20 parts of itaconic acid, 20 parts of hydroxyethyl acrylate and
20 parts of acrylamide, in accordance with this invention, had viscosities
less than about 600 cps at 30 percent total solids content at a pH value
of up to about pH 6 and viscosities less than about 1200 cps at 35 percent
total solids content at pH 6. Wet tensile strengths generally were
equivalent to those of the binder utilizing a solution polymer.
Since many latexes provided commercially have pH values as low as about pH
2.0, the effect of pH on wet tensile strength and viscosity is of concern.
The aqueous dispersions of the present invention normally have a pH within
the range between about pH 1.0 to about pH 4.5. A blended binder
composition of acidic latex and acidic dispersion will produce some degree
of wet tensile strength. However, it has been found that neutralizing the
binder composition with a base, such as sodium hydroxide, or, preferably,
with ammonium hydroxide to a value of between about pH 4.0 and about pH
9.0, will produce final binder compositions having considerably improved
wet tensile strength. On the other hand, as the pH value rises, the
viscosity tends to increase. It is, therefore, usually advisable to
provide a binder composition within a range of about pH 4 to about pH 6 in
order to maximize the wet tensile strength while maintaining the viscosity
within acceptable limits.
The invention is further described by the following examples which are
illustrative of specific modes of practicing the invention and are not
intended as limiting the scope of the invention as defined in the claims.
All percentages are by weight unless otherwise specified.
EXAMPLE 1
A mixture comprised of 23.6 g acrylamide, 23.6 g butyl acrylate, 23.6 g
2-hydroxyethyl acrylate, 23.6 g itaconic acid and 4.7 g Siponate A-246L,
an alpha-olefin sulfonate surfactant available from Alcolac, Inc.,
Baltimore, Md., was emulsified in 547 cc of deionized water and heated to
a temperature of 75.degree. C. A solution of initiator comprised of 0.9 g
sodium persulfate dissolved in 13 cc of deionized water was added. The
resulting emulsion was then heated at 75.degree. C. for 3 hours with
stirring, and the pH value adjusted to pH 4.0-5.0 with concentrated
ammonium hydroxide. After cooling and filtering, 5 percent, by weight, of
the resulting aqueous dispersion was admixed with a non-formaldehyde
emitting carboxylated SBR copolymer latex comprised of 60 percent styrene,
40 percent butadiene and 1 percent itaconic acid with 2.0 to 5.0 percent
methyl acryloamidoglycolate methyl ether (MAGME) as cross-linker. The
resulting binder composition was then neutralized with concentrated
ammonia to pH 6.0 and diluted with deionized water to a non-volatile
solids content of 12 percent. For comparison purposes, a binder
composition utilizing the same SBR latex and 5 percent of an aqueous
solution polymer comprising 33 percent acrylamide, 33 percent
2-hydroxyethyl acrylate and 33 percent itaconic acid was prepared.
To determine the strength improvement of the binder of the present
invention over the binder utlizing the solution polymer, sets of one-inch
wide, nonwoven, randomly-oriented cellulose strips were padded in the
binder compositions described above to obtain a binder add-on of
approximately 10 percent. Padding is the process of dipping or saturating
a substrate in a bath and squeezing off the excess liquid with nip
rollers. The binder-containing strips were cured at 188.degree. C. for
periods of 4 seconds, 6 seconds, and 8 seconds, and then dipped in a 1
percent solution of Aerosol OT, a sodium octyl sulfosuccinate wetting
agent available from American Cyanamid, Wayne, N.J. The wet tensile
strengths were measured with the results shown in Table 1.
TABLE 1
______________________________________
Wet Tensile Strength (psi)
4 Sec. 6 Sec. 8 Sec.
______________________________________
Binder System Cure Cure Cure
______________________________________
SBR + Solution Polymer
4.5 6.6 6.6
SBR + Dispersion of
4.8 6.7 7.1
Emulsion Polymer (this
invention)
______________________________________
It can be seen that the wet tensile strengths obtained using the polymer
dispersion of the present invention with a styrene-butadiene latex were
higher than those obtained using a solution polymer with a
styrene-butadiene latex.
The following example illustrates the preparation and properties of several
alternative emulsion copolymer dispersions in accordance with the present
invention.
EXAMPLE 2
The procedure of Example 1 was followed except that different mixtures of
monomers and monomer concentrations and different surfactants were used.
The formulations and physical properties of the emulsion polymer
dispersions obtained are shown in Table 2, in which concentrations of
ingredients are expressed as parts per hundred parts total monomer (phm).
TABLE 2
__________________________________________________________________________
Monomer.sup.2 Total
Part.
Run
Surfactant.sup.1
S BA EHA IA MA HEA HPMA
AMD Solids
Size
Visc.
No.
(phm) (phm)
(phm)
(phm)
(phm)
(phm)
(phm)
(phm)
(phm)
pH
(%) (nm)
(cps)
__________________________________________________________________________
1 5.0 A 0.0 40.0
0.0 30.0
0.0 30.0
0.0 0.0
1.7
13.1
157 7
2 5.0 A 0.0 40.0
0.0 0.0
30.0
30.0
0.0 0.0
1.0
11.1
111 8
3 5.0 A 40.0
0.0
0.0 20.0
0.0 20.0
0.0 20.0
3.0
13.5
847 8
4 5.0 A 0.0 40.0
0.0 20.0
0.0 0.0
20.0
20.0
4.1
14.0
291 9
5 5.0 A 0.0 40.0
0.0 20.0
0.0 20.0
0.0 20.0
3.4
15.2
166 10
6 5.0 A 0.0 40.0
0.0 20.0
0.0 0.0
20.0.sup.4
20.0
4.2
13.3
184 11
7 5.0 A 30.0
0.0
0.0 23.2
0.0 23.2
0.0 23.2
3.1
14.2
563 12
8 5.0 A 0.0 40.0
0.0 20.0
0.0 20.0
0.0 20.0
3.5
14.3
167 14
9 5.0 A 0.0 40.0
0.0 20.0
0.0 20.0
0.0 20.0
4.0
14.4
180 15
10 5.0 A 0.0 40.0
0.0 0.0
20.0
0.0
20.0
20.0
1.7
10.8
748 15
11 5.0 A 0.0 40.0
0.0 0.0
20.0
0.0
20.0.sup.4
20.0
1.9
15.0
2067
15
12 5.0 A 0.0 35.0
0.0 21.7
0.0 21.7
0.0 21.7
3.9
14.4
191 16
13 5.0 A 0.0 0.0
30.0
23.3
0.0 23.3
0.0 23.3
3.8
14.4
185 16
14 5.0 A 0.0 30.0
0.0 23.3
0.0 23.3
0.0 23.3
3.9
14.4
201 17
15 5.0 A 0.0 40.0
0.0 0.0
20.0
20.0
0.0 20.0
1.7
13.0
367 19
16 5.0 A 0.0 0.0
20.0
26.7
0.0 26.7
0.0 26.7
4.0
14.1
190 19
17 5.0 A 0.0 25.0
0.0 25.0
0.0 25.0
0.0 25.0
3.7
13.9
206 22
18 5.0 B 0.0 30.0
0.0 23.2
0.0 23.3
0.0 23.3
3.8
14.4
251 27
19 5.0 A 0.0 20.0
0.0 26.7
0.0 26.7
0.0 26.7
3.6
14.3
216 28
__________________________________________________________________________
Notes for Table:
1. A = Dowfax 2A1, sulfonated biphenyl ether, available from Dow Chemical
Co., Midland, Michigan B = Aerosol OT, dioctyl sodium sulfosuccinate,
available from American Cyanamid Co., Wayne, New Jersey
2. S = Styrene, BA = butyl acrylate, EHA = 2ethylhexyl acrylate, IA =
itaconic acid, MA = maleic acid, HEA = 2hydroxyethyl acrylate, HPMA =
hydroxypropyl methacrylate, AMD = acrylamide
3. Twostage batch reaction in which 2/3 of IA, HEA and AMD were added in
second stage along with an additional 0.5 phm of activator.
4. Monomer added by delay addition over 1.5 hr period.
The following example illustrates the viscosities of binders prepared using
the emulsion copolymer dispersions of the present invention compared to
binders prepared using Cymel-303, a typical formaldehyde emitting
cross-linker, binders prepared using MAGME, a typical non-formaldehyde
emitting composition, and binders prepared using the solution copolymers
described above.
EXAMPLE 3
Binders prepared using the formulations of Runs 7, 11 and 14 of Example 2
with a base SBR polymer latex comprised of 56.6 percent styrene, 37.7
percent butadiene, 4.7 percent methyl acryloamidoglycolate methyl ether
(MAGME) and 0.9 percent itaconic acid were compared, with respect to
viscosity, with a base SBR polymer latex; with a widely used reference
commercial cellulose binder composition comprising a carboxylated SBR
latex (53.4 percent butadiene, 43.7 percent styrene, 1.9 percent
N-methylol acrylamide and 0.5 percent each of acrylamide and itaconic
acid) cross-linked with 6 percent methoxymethyl melamine (Cymel-303), a
known formaldehyde emitter; with a binder composition utilizing the base
SBR polymer latex plus 5 percent of a solution polymer prepared from 33
percent acrylamide, 33 percent hydroxyethyl acrylamide and 33 percent
itaconic acid. Each of the aqueous dispersions of emulsion polymers of
Runs 7, 11 and 14 were admixed with the base SBR latex in a concentration
of 5 percent. The viscosity of each of the binder systems was measured at
30 and 35 percent total solids content and at pH 4, pH 6, and pH 8. The
results are shown in Table 3.
TABLE 3
______________________________________
Viscosity as a
Total Function of pH
Binder System Solids (%)
pH 4 pH 6 pH 8
______________________________________
Commerical carboxylated
35 -- -- 20
SBR latex cross-linked
30 -- -- 10
with Cymel-303
Carboxylated SBR latex
35 2360 3605 3980
cross-linked with MAGME
30 715 1630 1815
plus solution copolymer
Carboxylated SBR latex
35 20 16 --
cross-linked with MAGME
30 17 11 --
plus aqueous emulsion
copolymer dispersion
of Run 3
Carboxylated SBR latex
35 116 171 --
cross-linked with MAGME
30 14 19 --
plus aqueous emulsion
copolymer dispersion
of Run 7
Carboxylated SBR latex
35 104 454 926
cross-linked with MAGME
30 30 39 174
plus aqueous emulsion
copolymer dispersion
of Run 9
Carboxylated SBR latex
35 29 900 1010
cross-linked with MAGME
30 15 434 503
plus aqueous emulsion
copolymer dispersion
of Run 13
Carboxylated SBR latex
35 260 1148 1280
cross-linked with MAGME
30 15 591 696
plus aqueous emulsion
copolymer dispersion
of Run 16
______________________________________
It should be noted that the binders utilizing the aqueous dispersions of
emulsion copolymers of Runs 3, 7, 9, 13 and 16, representative aqueous
emulsion copolymer dispersions of the present invention, have lower
viscosities at all pH values than the corresponding binder systems
utilizing a solution polymer.
The following example illustrates the wet tensile strength of the aqueous
emulsion copolymers of the present invention compared to the binders
described in Example 3 and to the base SBR latex.
EXAMPLE 4
Several of the binder systems described in Example 3 were tested for
tensile strength after a 6 second cure at 188.degree. C. and after a 180
second cure at 149.degree. C. and compared to the base SBR latex. The
results obtained are shown in Table 4.
TABLE 4
______________________________________
Wet Tensile Strength (psi)
Cured 6 sec.
Cured 180 sec.
Binder System at 188.degree. C.
at 149.degree. C.
______________________________________
Commerical carboxylated
10.0 9.8
SBR latex cross-linked
with Cymel-303
Carboxylated SBR latex
5.2 6.2
cross-linked with MAGME
Carboxylated SBR latex
7.6 9.5
cross-linked with MAGME
plus solution copolymer
Carboxylated SBR latex
6.2 7.2
cross-linked with MAGME
plus aqueous emulsion
copolymer dispersion of
Run 9
Carboxylated SBR latex
7.4 8.0
cross-linked with MAGME
plus aqueous emulsion
copolymer dispersion of
Run 13
Carboxylated SBR latex
6.6 7.6
cross-linked with MAGME
plus aqueous emulsion
copolymer dispersion of
Run 16
______________________________________
EXAMPLE 5
Several other binder systems described in Example 3 were tested for tensile
strength after a 6 second cure at 188.degree. C., an 8 second cure at
188.degree. C. and a 180 second cure at 149.degree. C. and compared to the
base SBR latex. The results obtained are shown in Table 5.
TABLE 5
______________________________________
Wet Tensile Strength (psi)
Cured 6 Cured 8 Cured 180
sec. at sec. at sec. at
Binder System 188.degree. C.
188.degree. C.
149.degree. C.
______________________________________
Commercial carboxylated
8.6 9.2 9.4
SBR latex cross-linked
with Cymel-303
Carboxylated SBR latex
5.5 5.4 5.6
cross-linked with MAGME
Carboxylated SBR latex
7.2 7.7 10.2
cross-linked with MAGME
plus solution copolymer
Carboxylated SBR latex
6.0 6.0 8.0
cross-linked with MAGME
plus aqueous emulsion
copolymer dispersion of
Run 3
Carboxylated SBR latex
5.6 6.3 8.1
cross-linked with MAGME
plus aqueous emulsion
copolymer dispersion of
Run 7
______________________________________
Note that the wet tensile strengths of the binder system utilizing the
aqueous emulsion copolymer dispersion of the present invention are in all
cases higher than those obtained using a carboxylated SBR latex
cross-linked with MAGME. In addition, the results obtained are similar to
the results obtained using a solution copolymer but with a viscosity (See
Table 3) which is approximately one-third or less of the viscosity of the
binder system utilizing the solution copolymer. Furthermore, the wet
tensile strengths are as high as about 85 percent of the wet tensile
strengths obtained using a commercial carboxylated SBR latex cross-linked
with Cymel-303, a known formaldehyde emitter.
This invention may be embodied in other forms without departing from the
spirit or essential characteristics thereof. For example, it is recognized
that, while the description of the present invention and the preferred
embodiments thereof are directed toward fast curing non-formaldehyde
emitting binders, there may be applications wherein formaldehyde emission
is not of concern and where the use of one or more formaldehyde emitting
cross-linkers or other constituents may be necessary or desirable in the
final binder composition. There may also be applications wherein a fast
cure is not essential. Consequently, the present embodiments and examples
are to be considered only as being illustrative and not restricted, with
the scope of the invention being indicated by the appended claims. All
embodiments which come within the scope and equivalency of the claims are,
therefore, intended to be embraced therein.
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